Documentation

A random variable returning an arbitrary element of the given list.
Every element has equal probability of being chosen. Because it is a
pure RVar it has no memory - that is, it "draws with replacement."

A random variable that shuffles a list of a known length (or a list
prefix of the specified length). Useful for shuffling large lists when
the length is known in advance. Avoids needing to traverse the list to
discover its length. Each ordering has equal probability.